Many proposals have been made heretofore for interlocking but separable plastic seam members for a wide variety of purposes and particularly for holding jacketing assembled about ducting. Typically, such seam members include a mounting web heat fusible to the lateral edges of plastic sheeting. Customarily such mounting web are attached to the outer surface of the plastic in order that one edge of the sheeting will underlie and extend across the inner side of the seam to safeguard against the material being enclosed interfering with the closure of the seam.
Prior proposals for separable seaming and jacketing usable therewith, fail to meet appearance and sanitation requirements of certain operating environments having need for exacting cleanliness, sanitation and appearance standards, as for example, in hospitals, food processing operations, ultra clean rooms for many manufacturing and assembly operations, and the like. In such environments it is mandatory that ducting and other components be jacketed with flexible main bodies having a highly smooth, nonporous outer surface and an inner main body material of flexible material satisfied by various types of fusible plastic sheeting suitably laminated to the high spec outer surface. An outer material satisfactorily meeting these requirements is not heat fusible to the plastic seam members. If the seam members are heat fused to the inner surface of such a laminated material then the full thickness of the sheeting lies externally of the seam and the lateral edge of the sheeting is closely spaced from the innernesting portions of the seam members when closed, thereby providing a shoulder and a substantially inaccessible recess in which foreign material can collect and render the jacketing unsightly and unacceptable in environments required to meet strict cleanliness and sanitary standards.